Effect of Ga and Se addition on the “near-surface” photo-response of new Ge-based chalcogenide glasses under IR femtosecond laser exposure

In this paper, we report results of a systematic study to evaluate the relationship between compositional variation and the photo-response of Gallium containing sulfo-selenide glasses upon IR femtosecond laser exposure. We show that IR femtosecond laser irradiation in this system results in near-surface photo-expansion, which based on micro-Raman spectroscopy, has been related to an increased connection of GeS4 units to form corner sharing GeS4/2 units with a concurrent formation of S–S bridges. The lower surface photo-expansion of the Ga- containing sulfide and sulfo-selenide glasses compared to that of the Ga-free sulfide and sulfo-selenide glasses has been related to the presence of GaS4 and Se–Se isolated units in the germanate glass network which are expected to restrict the connection between GeS4 units during laser exposure. Such mechanistic understanding of material modification opens the pathway towards the laser writing of active photonic devices in the near-surface of these glasses.